Describing individual variation in local sweating during exercise in a temperate environment

It has been previously demonstrated that the individual variation in whole-body sweat rate is described by differences in each participant's heat balance status. It was hypothesized that the individual variation in local sweat rate of the forehead (LSR(head)) and forearm (LSR(arm)) would be similarly described using a whole-body heat balance approach, specifically the ratio of evaporation required for heat balance relative to the maximum evaporation possible (i.e. E (req):E (max)). Twelve males cycled at 60% [Formula: see text] for 60 min at 24.9 ± 0.5°C, 31 ± 14% relative humidity. Rectal (T (re)) and aural canal (T (au)) temperatures as well as mean skin temperature ([Formula: see text]), metabolic energy expenditure (M) and rate of external work (W) were measured throughout. In addition, whole-body sweat rate at steady state (WBSR(ss)) was estimated using the change in body mass over the last 15 min of exercise, with LSR(head) and LSR(arm) estimated using technical absorbent patches applied between the 50th and 55th minute. WBSR(ss) significantly correlated with M-W (r = 0.66, P = 0.021), E (req) (r = 0.69, P = 0.013) and E (req):E (max) (r = 0.87, P < 0.001); LSR(head) was significantly correlated with E (req):E (max) (r = 0.82, P = 0.001), but not M-W (r = 0.31, P = 0.328) or E (req) (r = 0.38, P = 0.227); and LSR(arm) significantly correlated with E (req) (r = 0.62, P = 0.031) and E (req):E (max) (r = 0.78, P = 0.003) but not M-W (r = 0.56, P = 0.059). None of WBSR(ss), LSR(head) or LSR(arm) significantly correlated with any variations in T (re), T (au) or [Formula: see text] (i.e. 0.8T (re) + 0.2[Formula: see text]). Secondary analyses also demonstrated that both LSR(head) (r = 0.79, P = 0.002) and LSR(arm) (r = 0.89, P < 0.001) correlated with WBSR(ss). In conclusion, the individual variation in WBSR(ss), LSR(head) and LSR(arm) is described by the ratio of E (req) relative to E (max).